2,371 research outputs found
Chiral zero modes of the SU(n) Wess-Zumino-Novikov-Witten model
We define the chiral zero modes' phase space of the G=SU(n)
Wess-Zumino-Novikov-Witten model as an (n-1)(n+2)-dimensional manifold M_q
equipped with a symplectic form involving a special 2-form - the Wess-Zumino
(WZ) term - which depends on the monodromy M. This classical system exhibits a
Poisson-Lie symmetry that evolves upon quantization into an U_q(sl_n) symmetry
for q a primitive even root of 1. For each constant solution of the classical
Yang-Baxter equation we write down explicitly a corresponding WZ term and
invert the symplectic form thus computing the Poisson bivector of the system.
The resulting Poisson brackets appear as the classical counterpart of the
exchange relations of the quantum matrix algebra studied previously. We argue
that it is advantageous to equate the determinant D of the zero modes' matrix
to a pseudoinvariant under permutations q-polynomial in the SU(n) weights,
rather than to adopt the familiar convention D=1.Comment: 30 pages, LaTeX, uses amsfonts; v.2 - small corrections, Appendix and
a reference added; v.3 - amended version for J. Phys.
A Quantum Gauge Group Approach to the 2D SU(n) WZNW Model
The canonical quantization of the WZNW model provides a complete set of
exchange relations in the enlarged chiral state spaces that include the Gauss
components of the monodromy matrices. Regarded as new dynamical variables, the
elements of the latter cannot be identified -- they satisfy different exchange
relations. Accordingly, the two dimensional theory expressed in terms of the
left and right movers' fields does not automatically respect monodromy
invariance. Continuing our recent analysis of the problem by gauge theory
methods we conclude that physical states (on which the two dimensional field
acts as a single valued operator) are invariant under the (permuted) coproduct
of the left and right . They satisfy additional constraints fully
described for n=2.Comment: 10 pages, LATEX (Proposition 4.2 corrected, one reference added
Modelling background charge rearrangements near single-electron transistors as a Poisson process
Background charge rearrangements in metallic single-electron transistors are
modelled in two-level tunnelling systems as a Poisson process with a scale
parameter as only variable. The model explains the recent observation of
asymmetric Coulomb blockade peak spacing distributions in metallic
single-electron transistors. From the scale parameter we estimate the average
size of the tunnelling systems, their density of states, and the height of
their energy barrier. We conclude that the observed background charge
rearrangements predominantly take place in the substrate of the single-electron
transistor.Comment: 7 pages, 2 eps figures, used epl.cls macro include
Properties and occurrence rates of exoplanet candidates as a function of host star metallicity from the DR25 catalog
Correlations between the occurrence rate of exoplanets and their host star
properties provide important clues about the planet formation processes. We
studied the dependence of the observed properties of exoplanets (radius, mass,
and orbital period) as a function of their host star metallicity. We analyzed
the planetary radii and orbital periods of over 2800 candidates from
the latest data release DR25 (Q1-Q17) with revised planetary radii
based on ~DR2 as a function of host star metallicity (from the Q1-Q17
(DR25) stellar and planet catalog). With a much larger sample and improved
radius measurements, we are able to reconfirm previous results in the
literature. We show that the average metallicity of the host star increases as
the radius of the planet increases. We demonstrate this by first calculating
the average host star metallicity for different radius bins and then
supplementing these results by calculating the occurrence rate as a function of
planetary radius and host star metallicity. We find a similar trend between
host star metallicity and planet mass: the average host star metallicity
increases with increasing planet mass. This trend, however, reverses for masses
: host star metallicity drops with increasing planetary
mass. We further examined the correlation between the host star metallicity and
the orbital period of the planet. We find that for planets with orbital periods
less than 10 days, the average metallicity of the host star is higher than that
for planets with periods greater than 10 days.Comment: 14 pages, 13 Figures, Accepted for publication in The Astronomical
Journa
Is depression a real risk factor for acute myocardial infarction mortality? A retrospective cohort study
Background: Depression has been associated with a higher risk of cardiovascular events and a higher mortality in patients with one or more comorbidities. This study investigated whether continuative use of antidepressants (ADs), considered as a proxy of a state of depression, prior to acute myocardial infarction (AMI) is associated with a higher mortality afterwards. The outcome to assess was mortality by AD use. Methods: A retrospective cohort study was conducted in the Veneto Region on hospital discharge records with a primary diagnosis of AMI in 2002-2015. Subsequent deaths were ascertained from mortality records. Drug purchases were used to identify AD users. A descriptive analysis was conducted on patients' demographics and clinical data. Survival after discharge was assessed with a Kaplan-Meier survival analysis and Cox's multiple regression model. Results: Among 3985 hospital discharge records considered, 349 (8.8%) patients were classified as AD users'. The mean AMI-related hospitalization rate was 164.8/100,000 population/year, and declined significantly from 204.9 in 2002 to 130.0 in 2015, but only for AD users (-40.4%). The mean overall follow-up was 4.64.1years. Overall, 523 patients (13.1%) died within 30days of their AMI. The remainder survived a mean 5.3 +/- 4.0years. After adjusting for potential confounders, use of antidepressants was independently associated with mortality (adj OR=1.75, 95% CI: 1.40-2.19). Conclusions: Our findings show that AD users hospitalized for AMI have a worse prognosis in terms of mortality. The use of routinely-available records can prove an efficient way to monitor trends in the state of health of specific subpopulations, enabling the early identification of AMI survivors with a history of antidepressant use
Coulomb oscillations in three-layer graphene nanostructures
We present transport measurements on a tunable three-layer graphene single
electron transistor (SET). The device consists of an etched three-layer
graphene flake with two narrow constrictions separating the island from source
and drain contacts. Three lateral graphene gates are used to electrostatically
tune the device. An individual three-layer graphene constriction has been
investigated separately showing a transport gap near the charge neutrality
point. The graphene tunneling barriers show a strongly nonmonotonic coupling as
function of gate voltage indicating the presence of localized states in the
constrictions. We show Coulomb oscillations and Coulomb diamond measurements
proving the functionality of the graphene SET. A charging energy of meV is extracted.Comment: 10 pages, 6 figure
Chiral zero modes of the SU(n) WZNW model
We define the chiral zero modes' phase space of the G=SU(n) Wess-Zumino-Novikov-Witten (WZNW) model as an (n-1)(n+2)-dimensional manifold M_q equipped with a symplectic form involving a special 2-form - the Wess-Zumino (WZ) term - which depends on the monodromy M. This classical system exhibits a Poisson-Lie symmetry that evolves upon quantization into an U_q(sl_n) symmetry for q a primitive even root of 1. For each constant solution of the classical Yang-Baxter equation (CYBE) we write down explicitly a corresponding WZ term and invert the symplectic form thus computing the Poisson bivector of the system. The resulting Poisson brackets appear as the classical counterpart of the exchange relations of the quantum matrix algebra studied previously. We argue that it is advantageous to equate the determinant D of the zero modes' matrix to a pseudoinvariant under permutations polynomial in the SU(n) weights, rather than to adopt the familiar convention D=1
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